ABSTRACT
AIM:To study the effect of Panax quinquefolium saponin (PQS) on cardiomyocyte apoptosis in-duced by thapsigargin ( TG) .METHODS:Primary cultured cardiomyocytes from neonatal SD rats were divided into con-trol group, TG group, PQS (40 mg/L, 80 mg/L and 160 mg/L) +TG group, si-PERK+TG group, and mock+TG group.The cells were treated with 1 μmol/L TG for 24 h to induce apoptosis.The PERK gene in the cardiomyocytes was knocked down by RNAi.The cell viability was detected by CCK-8 assay.Apoptosis was analyzed by flow cytometry.Wes-tern blotting was used to determine the expression of ERS molecules GRP78, CRT, ATF4 and CHOP, anti-apoptosis pro-tein Bcl-2 and pro-apoptosis protein Bax.RESULTS: Compared with control group, TG significantly and the apoptosis, reduced the cell viability (P<0.05), increased the phosphorylation of PERK and eIF2α, increased the expression of GRP78, CRT, ATF4, CHOP and pro-apoptosis protein Bax, and decreased the expression of anti-apoptosis protein Bcl-2 (P<0.05).Compared with TG group, PQS treatment (160 mg/L) significantly reduced the apoptosis and increased the cell viability (P<0.05).All the 3 different concentrations of PQS significantly increased the expression of anti-apoptosis protein Bcl-2 and reduced the expression of pro-apoptosis protein Bax (P<0.05) in a dose-dependent manner.PQS pre-treatment and knockdown of PERK both reduced the protein levels of GRP78, CRT, PERK, p-PERK, eIF2α, p-eIF2α, ATF4, CHOP and pro-apoptosis protein Bax, and increased the expression of anti-apoptosis protein Bcl-2 (P<0.05). CONCLUSION:PQS at concentration of 160 mg/L attenuated cardiomyocyte apoptosis induced by TG.PQS had the simi-lar effect as PERK knockdown on cardiomyocyte apoptosis.The mechanism may be associated with inhibiting PERK-eIF2α-ATF4-CHOP pathway of ERS-related apoptosis.
ABSTRACT
AIM:To investigate whether mitochondrial membrane potential (ΔΨm ) and the mitochondrial ap-optotic pathway are involved in the protective mechanism of Panax quinquefolium saponin ( PQS) against cardiomyocyte ap-optosis after ischemia/reperfusion ( I/R) injury in rat myocardium .METHODS: Ninety healthy male SD rats were ran-domly divided into sham group , I/R group, PQS (200 mg· kg -1 · d-1 ) +I/R group, cyclosporine A ( CsA) group, CsA (10 mg· kg-1 ) +I/R group and PQS +CsA +I/R group.The model of myocardial I/R injury in vivo was established by ligating the left anterior descending artery ( LAD) for 30 min followed by 120 min of reperfusion in the rats .The serum ac-tivity of lactate dehydrogenase ( LDH ) was measured by automatic chemistry analyzer .The myocardial infarct size was measured by Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) staining.Cardiomyocyte apoptosis was detected by in situ TDT-mediated dUTP nick end labeling (TUNEL).The protein levels of Bcl-2, Bax, cleaved caspase-3 and cytosol-ic cytochrome C were determined by Western blotting .ΔΨm was measured by laser scanning confocal microscopy and fluo-rescence microplate reader .RESULTS:Compared with I/R group, the serum content of LDH ,the infarction size in PQS+I/R group, CsA+I/R group and PQS +CsA+I/R group and the myocardial apoptotic index were decreased .Compared with I/R group, the fluorescence intensity of mitochondria after JC-1 staining was enhanced in PQS +I/R group, CsA+I/R group and PQS+CsA+I/R group, and the relative fluorescence units (RFU) ofΔΨm were improved in those 3 groups. In PQS+I/R group, CsA+I/R group and PQS+CsA+I/R group, the protein expression of Bcl-2 was increased, and that of Bax was decreased compared with I/R group.Moreover, in those 3 groups, the protein levels of cleaved-caspase-3 and cytosolic cytochrome C were decreased compared to I /R group, respectively.CONCLUSION:PQS attenuates myocardial injury and cardiomyocyte apoptosis during I /R, and the protective mechanisms of PQS were associated with the modulation ofΔΨm and the inhibition of mitochondrial apoptosis pathway .